Monday, June 4, 2007 - 4:00 PM
45

Seasonal and spatial variability in nutrient availability and nutrient uptake in streams from a Mediterranean catchment

Daniel Von Schiller1, Eugènia Martí1, Joan L. Riera2, Miquel Ribot1, Alba Argerich2, Paula Fonolla1, Jane C. Marks3, and Francesc Sabater2. (1) Limnology Group, Centre d'Estudis Avançats de Blanes (CSIC), Accés a la Cala Sant Francesc 14, Blanes (Girona), 17300, Spain, (2) Departament d'Ecologia, Universitat de Barcelona, Av. Diagonal 645, Barcelona, 08028, Spain, (3) Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011

Despite intense research on stream nutrient retention, we still know little about its temporal and spatial variability within a catchment. In this study we examined how stream nutrient uptake varied seasonally and among sites in La Tordera catchment (NE Spain), with special emphasis on concomitant changes in nutrient availability. Short-term injections of ammonium and phosphate were conducted in 13 streams draining sub-catchments subjected to different land uses in spring 2006. Additionally, in 3 reference forested streams injections were performed monthly from autumn 2004 to summer 2006. Temporal variation in nutrient availability in the reference streams was high, covering a similar concentration range as that found across all streams in one season. The range of uptake velocities (Vf) measured over time in the reference streams was also wide and comparable to that measured across all streams. Both temporal variation of phosphate-Vf in the reference streams and spatial variation across all streams were negatively related to phosphate concentration. In contrast, ammonium-Vf and ammonium concentration were only negatively correlated across streams. Results indicate that variation in nutrient availability driven by both seasonal and land use changes can influence nutrient uptake in highly dynamic Mediterranean streams.

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